see [1]}. Moreover, if \(a\in {\rm BMO}(\mathbb {R}^d)\) , then for a cube \(Q\)  and a suitable function \(f\) , it follows from (REF ) and the John-Nirenberg inequality that
\(\int _{Q}|a(x)-\langle a\rangle ||f(x)|dx\lesssim \Vert a\Vert _{{\rm BMO}(\mathbb {R}^d)}|Q|\Vert f\Vert _{L\log L,\,Q}.\) 
